It is common for infant cup valve assemblies, and their respective components, to be formed from various types of plastic, and as such injection moulding is a common manufacturing method. However, valve assemblies often comprise complex arrangements of small components. This has traditionally led to the components being moulded separately and subsequently being assembled during manufacture to form the completed valve assembly. Thus, different moulds are required depending on the size, form and desired type of material to be used when forming the valve assembly components. These parts may then need to be glued or otherwise coupled together during manufacture. For example, in EP2134617B1, there is described a no-spill infant cup valve assembly. The assembly, however, consists of at least two separately moulded parts, and therefore requires at least one assembly step during the manufacturing process. In addition, the valve requires the user to reassemble it by coordinating small locating features every time the valve is removed for cleaning; failure to reassemble the valve correctly results in liquid leaking from the cup. Clearly, therefore, there is a need for both an improved method of manufacture, and a simpler valve assembly, which can benefit from reduced cost and manufacturing time.
One type of well-known drinking cup is the so-called no-spill drinking cup, suitable for infant usage. The aim of a no-spill cup and associated valve is to provide a cup which allows the contents of the cup to escape through the valve only upon usage by the user, for example via the application of suction. Suction-operated valves may sometimes be referred to as ‘demand valves’ to differentiate them from other non-spill valves, such as ‘bite valves’, which are opened by the user temporarily deforming the closure device with their teeth or lips to allow liquid to escape. A demand valve incorporated into a no-spill cup should therefore prevent the contents of the cup from escaping when for example when the cup is vigorously shaken, when the cup is inverted, or when the cup is accidentally dropped. However, there is always a risk that such a valve having, for example, a flexible component designed to move in response to a pressure differential can be easily deformed by the impact of liquid on the component, which often occurs during such shaking or dropping. Thus, undesirable leakage can occur. Conversely, a user should not have to apply excessive suction in order to open the valve. There is therefore a need in the art for a valve assembly suitable for a drinking cup in which an improved seal is provided, whilst ensuring that a user is not inconvenienced when using the drinking cup.
In EP2134617B1, the closure element relies on a stem that passes through the same channel that the liquid flows through. There is therefore only a small space around the stem for liquid to flow and flow rate is limited accordingly. If the stem were made narrower (to allow more water to flow around it), there may not be sufficient closure force on the ‘mushroom head’ to seal the valve closed, and the mushroom head may become difficult to install by pushing through the channel. Alternatively, if the mushroom head and liquid channel were made larger relative to the stem, to accommodate more flow, then the head may become too flexible to cap the channel inlet.
It is also a known problem with demand valves that control liquid flow via a slit in a flexible material that they have a tendency to ‘heal’ (see for example EP1014839B1). This can affect, for example, slits in silicone diaphragms and may mean that the material can repair itself during shipping so that the user finds difficulty in getting the valve to work when they first try to use it.
The present invention seeks to address these and other disadvantages encountered in the prior art, by providing an improved valve assembly for a drinking cup.